The invention relates to a switchable component advantageously constructed as a tappet or support element in a valve train of an internal combustion engine, with a housing in whose borehole an inner element is held so that it can telescope, wherein at least one coupling piston guided by an anti-rotation locking device sits in a radial borehole of the inner element in a decoupled case, with a section that is flattened in some areas being inherent in this coupling piston on one axial side starting from its outer end, wherein the borehole of the housing has a window or an annular groove/an annular-groove segment with a complementary engagement surface against which, in a coupled case, the coupling piston can be displaced with its flattened section when passing through the cam base circle and wherein an edge between the outer end and the flattened section of the coupling piston is provided with a bevel.
DE 10 2005 020 580 A1 discloses a switchable component constructed as a roller tappet whose coupling piston is bulged cylindrically in the section of an edge between its outer end and flattened section. An anti-rotation locking device for the coupling piston is created by the annular element emerging from FIG. 2 of the document noted above, with this annular element lying underneath the flattened section of the coupling piston and being guided on the outer shell of the inner element. The measure named above should avoid a two-point contact in the case of unavoidable tilting of the coupling piston on its engagement surface in the housing. The coupling region in the prior art named above, however, must have fine tolerances, which is extremely complicated, in order to always guarantee that, for coupling, an upper edge of the annular element is slightly higher as shown than the opposite engagement surface of the housing of the coupling piston when passing through the cam base circle and internal stop position of the inner element. In this way, even for a maximum, undesired twisting of the coupling piston, its secure, unimpaired travel into the coupled position is guaranteed and at the same time it is prevented that this impacts with an edge section of its edge on the engagement surface of the housing.
A goal of reducing the manufacturing costs in mass production, however, necessarily also leads to the tolerances becoming less fine or to the selection of manufacturing processes that are associated with a greater deviation from the desired dimensions of the components. In the case of a switchable component according to DE 10 2005 020 580 A1, for the most unfavorable tolerance position, this has the result that, in a stop position of the inner element (passing through the cam base circle), an upper edge of its annular element is lower than the engagement surface of the housing and the coupling piston twisted to a maximum in its holder of the inner element forms a spring-force-loaded contact with an edge region on the inner edge of the engagement surface, without reaching its coupled position. The latter state leads at least to undesired wear of the coupling piston and also the inner edge of the engagement surface.
In addition, U.S. Pat. No. 6,578,535 B2 is also referenced. This document discloses, in FIG. 5, a coupling piston whose edge is provided with a planar bevel.